The present invention relates to a seat belt device for a vehicle comprising an inflatable bag portion which is provided at a seat belt for protecting an occupant and adapted to receive inflation air.
Conventionally, an air belt device for an automotive vehicle, in which a chamber is provided at the seat belt for protecting the occupant (passenger) on the vehicle and the like and there are provided a gas supply device to supply gas to the chamber and a detecting device to detect a vehicle crash state, wherein the gas is supplied to the chamber of the seat belt during the vehicle crash or the like, thereby inflating the seat belt, is known as shown in, for example, Japanese Patent Laid-Open Publication No. 2000-211461.
The above-described seat belt device has an advantage that the restraint force for the occupant which is generated by the seat belt for the occupant is so dispersed to a large extent that a too-large restraint force can be prevented from acting on the occupant partially. Namely, when the vehicle crash is detected, the gas supply device comprising an inflator is operated and supplies the gas into the chamber of the seat belt to inflate the seat belt. Meanwhile, there is a problem (disadvantage) that the inflator is generally not reused and thus once the inflator operates, it can not be reused. Accordingly, the determination of the inflation timing of the inflator needs to be conducted very carefully. Namely, if the inflator was operated at the timing a high likelihood of an occurrence of vehicle crash was detected, the inflator could not reused after that even though the vehicle crash had been avoided. Meanwhile, if the inflator was not operated until the real vehicle crash occurred, the proper protection of the occupant could not attained with the best inflation timing just before the real vehicle crash.